The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
One of the most widely utilized methods for characterization of the deep-level centers in semiconductors is deep-level transient spectroscopy or DLTS, first proposed by D. V. Lang. This technique is based on the measurement of junction capacitance transients due to thermal emission during a return to equilibrium conditions. However, conventional DLTS suffers from inherent setbacks. For example, if the series resistance of the device under test (DUT) is large, the capacitance transient may vary with the measurement frequency. If the resistivity is large enough, the capacitance transient might approximate the geometric capacitance for all measurement frequencies. For heavily doped materials, capacitance spectroscopy suffers from poor sensitivity. Furthermore, systems using a capacitance bridge for measurement are inherently slow. Improvements have been made in the U.S. Pat. No. 5,521,839 to Doolittle, et al., which described a DLTS system that employs a pseudo-logarithmic data storage scheme to digitize and analyze capacitance transients acquired from a test material.
Alternative measurement schemes have been proposed over the years. These methods rely on the direct measurement of thermally stimulated current transients, or the integration of these currents to yield charge transients. These systems rely on hardware based timing mechanisms to perform the required DLTS signal processing.